1. Field of the Invention
The present invention relates to a call reservation technique, and more particularly to a call reservation technique for a subscriber of another exchange utilizing a No. 7 signal.
2. Description of the Related Art
In earlier systems, a No. 7 signaling system has been applied and has served an electronic exchange as a common channel signaling system (hereinafter, referred to as a "CCS") recommended by the CCITT in 1980 for use in a telephone and data communication network as well as an integrated services digital network. When another exchange subscriber reserves and processes a call in some electronic exchanges, the call is processed in view of a call reattempt, not a call reservation. In other words, the electronic exchange has been embodied in such manner that, if an outgoing subscriber reserves an incoming subscriber call of another exchange, the outgoing exchange generates the call in a certain time interval and at certain times (for example, repeatedly at a two-minutes intervals and for ten times, the call being generated by the exchange), thereby connecting the call signal to the incoming subscriber if the incoming subscriber is in the idle state, or connecting the call signal to the outgoing subscriber if the incoming subscriber responds, or connecting a calling path if the outgoing subscriber responds. In the above system, when the call is generated in the exchange, the call is again generated beyond a certain time interval if the incoming subscriber is in the on-line state.
We have observed that the earlier call reservation method for another exchange subscriber has, among other, the following three notable disadvantages. First, there is the disadvantage in that the exchange of the outgoing subscriber repeatedly generates and transmits the call every predetermined time interval to the exchange of the incoming subscriber, thereby causing an unnecessary occupation of the inter-office trunk, and in which a load of the incoming exchange and the outgoing exchange (especially, the incoming exchange) is increased, thereby making it impossible to be in common use.
Second, even though the incoming subscriber is transferred to the idle state (that is, transferred to the calling ending state), the call cannot be immediately connected between the reserved outgoing subscriber and the incoming subscriber. This is because the incoming subscriber cannot be managed in the exchange of the outgoing subscriber. Third, if several outgoing subscribers reserve the call for an identical incoming subscriber, it is impossible to serve a call connection according to a reservation sequence since the call is again attempted in the exchange of the outgoing subscriber.
Other efforts in the art, for example, are those represented by U.S. Pat. No. 5,559,877 to Ash et al., entitled Automatic Provisioning Of Trucking And Routing Parameters In A Telecommunications Network, U.S. Pat. No. 5,550,914 to Clarke et al., entitled Communications Signaling Network Apparatus, U.S. Pat. No. 5,519,770 to Stein, entitled Enhanced Telephony Apparatus And System, U.S. Pat. No. 5,517,564 to slater et al., entitled Communication Apparatus And Method, U.S. Pat. No. 5,487,110 to Bray et al., entitled Apparatus And Method For Virtual Private Telephone Line With Automatic Ring Down, U.S. Pat. No. 5,384,840 to Blatchford et al., entitled Telecommunications System SS7 Signaling Interface With Signal Transfer Capability, U.S. Pat. No. 5,212,691 to Hokari, entitled Private Network With Means For Establishing Virtual Tie Trunks Between PRXs Through ISDN Public Network, and U.S. Pat. No. 5,249,222 to Pinard, entitled Host Remote Signaling In Telephone Systems. We have found however, that these efforts fail to teach or suggest an efficacious and reliable call reservation technique of the present invention: